Pre-treatments aimed at increasing the biodegradability of cosmetic industrial waste

This work investigated physic-chemical pre-treatments aimed at improving anaerobic digestion (AD) of cosmetic industrial waste produced by a plant belonging to L'Oréal Group. A mixture designed according to relative abundances of waste was considered: sludge from internal wastewater treatment plant (54%-wt), residues of shampoo/conditioner (31%-wt), mascara sludge (13%-wt), food waste (2%-wt). The mixture had 80% VS/TS and COD equal to 1240 mg O2/gVS; soluble fraction of COD was 22%. Investigated pre-treatments were: chemical, thermal, sonication and various combinations; their performances were assessed through the disintegration rate (DR, the increment of soluble COD due to the pre-treatment compared to the unaltered sample). Best results were achieved from TA - thermo-alkaline (120 min at 50 °C) with DR 64.4% and TAS - thermo-alkaline-sonication (15 min at 80 °C and 40 kHz) with DR 66.1%. The benefits of AD on pre-treated waste mixture were: 50% increase in methane yield (0.14 Nm3/kgVS) and 5-7%-wt reduction of waste amount. From technical, energy and economic viewpoints, the proposed technical solution can provide an interesting perspective, fully consistent with Circular Economy principles.